A wider variety of irons and steels (for example, low-alloy steel, carbon steel, stainless steel, and low-alloy cast iron) and non-ferrous metals having higher quality and development of steel making and processing techniques make it increasingly necessary to strictly control the amount of a trace element, particularly the amount of an element such as C, Si, S, P, Mn, and Ni, contained in a base material (for example, Fe, Cu, and Al). At a manufacturing plant or other similar sites for iron and steel materials and non-ferrous metal materials, a trace element contained in a base material is thus to be quantified in steel making and refining processes. An X-ray fluorescence analyzer is therefore now widely employed at such manufacturing plants and other places to quantitatively and qualitatively analyze an element contained in a sample by irradiating the sample with primary X-rays and detecting the intensity of fluorescent X-rays excited by the primary X-rays and discharged (for example, see Patent Document 1).
FIG. 3 is a schematic diagram of a configuration of a known simultaneous X-ray fluorescence analyzer. A simultaneous X-ray fluorescence analyzer 101 includes a preliminary exhaust chamber (sample chamber) 10, an analysis chamber 20 arranged above the preliminary exhaust chamber 10, a gate valve 30 arranged between the preliminary exhaust chamber 10 and the analysis chamber 20, a rotary pump (a vacuum pump) 40, a pressure sensor 41 detecting a pressure value p, valves 51 to 54, a control unit 160, a storage unit 70, and a display unit 71.
The preliminary exhaust chamber 10 includes a preliminary exhaust chamber housing 11 having an upper surface with an opening 11a and a lower surface with an opening 11b, and a sample holder 12 having a horizontal placement surface on which a sample S is placed. The sample holder 12 is movable between an upper position (a measuring position) at which the sample S is placed inside the preliminary exhaust chamber housing 11 while closing the opening 11b and a lower position (a replacement position) at which the sample S is placed outside the preliminary exhaust chamber housing 11. The inside of the preliminary exhaust chamber housing 11 is connected with an air release valve 54 and connected with the rotary pump 40, a pressure regulatory valve 53, and the pressure sensor 41 through an on-off valve 52.
The analysis chamber 20 includes an analysis chamber housing 21 having a lower surface with an opening 21a, an X-ray tube 22, and a detector 23. The X-ray tube 22 is installed to an upper portion of the analysis chamber housing 21 and is configured to emit primary X-rays toward the preliminary exhaust chamber 10 under the analysis chamber housing 21. The detector 23 has, for example, a housing with an introduction window, and the housing includes therein, for example, a semiconductor element for detecting the intensity of fluorescent X-rays. The detector 23 is installed to a right upper portion of the analysis chamber housing 21. The inside of the analysis chamber housing 21 is connected with the rotary pump 40, the pressure regulatory valve 53, and the pressure sensor 41 through the on-off valve 51.
The gate valve 30 has a horizontal plate body 31. The plate body 31 is movable between a left position (a disconnecting state) where the opening 11a of the preliminary exhaust chamber housing 11 and the opening 21a of the analysis chamber housing 21 are closed and a right position (a connecting state) where the opening 11a and the opening 21a communicate with each other.
A method of analyzing a plurality of samples S using the X-ray fluorescence analyzer 101 will now be described. FIG. 4 is a flowchart to illustrate the method of analysis. When analysis of a first sample S ends, the control unit 160 disconnects the inside of the analysis chamber housing 21 and the inside of the preliminary exhaust chamber housing 11 from each other by arranging the gate valve 30 at the left position (the disconnecting state) and disconnects the rotary pump 40 and the inside of the preliminary exhaust chamber housing 11 from each other by closing the on-off valve 52, in step S201 (a pressure regulation end step).
Next, in Step S202 (the pressure regulation end step), the control unit 160 disconnects the rotary pump 40 and the inside of the analysis chamber housing 21 from each other by closing the on-off valve 51 and closes the pressure regulatory valve 53. Next, in Step S203 (a sample ejecting step), the analyst opens the air release valve 54 to set the inside of the preliminary exhaust chamber housing 11 at atmospheric pressure.
Next, in Step S204 (the sample ejecting step), the analyst further replaces the first sample S with a second sample S by arranging the sample holder 12 at the lower position (the replacement position). In Step S205 (a sample introduction step), the analyst has the sample S placed inside the preliminary exhaust chamber housing 11 by arranging the sample holder 12 at the upper position (the measuring position).
With the sample holder 12 arranged at the upper position (the measuring position), in Step S206 (a preliminary exhaust step), the control unit 160 connects the rotary pump 40 and the inside of the preliminary exhaust chamber housing 11 together and changes a pressure value p2 in the preliminary exhaust chamber housing 11 from the atmospheric pressure to a rough vacuum (a predetermined pressure value P′ (for example, 50 Pa)) by closing the air release valve 54 and opening the on-off valve 52.
Next, in Step S207 (a pressure regulation starting step), when the pressure value p2 decreases to the predetermined pressure value P′ or less, the control unit 160 connects the rotary pump 40 and the inside of the analysis chamber housing 21 together by opening the on-off valve 51 and connects the inside of the analysis chamber housing 21 and the inside of the preliminary exhaust chamber housing 11 together by arranging the gate valve 30 at the right position (the connecting state). Subsequently, in Step S208 (the pressure regulation starting step), the control unit 160 exerts proportional-integral-derivative (PID) control using a PID parameter (a PID constant) stored in the storage unit 70 to adjust the degree of opening of the pressure regulatory valve 53 and has a pressure value p converge to a complete vacuum (a set vacuum value P (for example, 15 Pa)). In other words, the control unit 60 changes a pressure value p1 in the analysis chamber housing 21 and the pressure value p2 in the preliminary exhaust chamber housing 11 to the set vacuum value P.
Next, when the pressure value p stabilizes at the set vacuum value P, the control unit 160 irradiates the sample S with primary X-rays and detects the intensity of fluorescent X-rays generated from the sample S using the detector 23, in Step S209 (an analyzing step). Upon detection of the intensity of fluorescent X-rays, in Step S210 (the analyzing step), the control unit 160 stops irradiating the sample S with the primary X-rays to end the analysis, and displays results of the analysis on the display unit 71.